1. Field of the Invention
This invention relates to an insulated-gate semiconductor device, and more particularly to an insulated-gate semiconductor device which is effective as a protective device for the insulated gate of an insulated-gate FET.
2. Description of the Prior Art
Several expedients have heretofore been proposed as protective devices for protecting the insulated gate of an insulated-gate FET from electrostatic breakdown etc. Most generally used among the expedients is a diode assembly of the back-to-back structure of the pnp-type or npn-type which is respectively used for the n-channel or p-channel insulated-gate FET. However, in the case where the inverse connected diodes are of the npn-type, a parasitic npn-type transistor turns "on," and a negative resistance occurs in the voltage--current characteristic of the protective device, so that the device becomes astable.